LowPower library usage in Arduino - Mini Project: Build & Apply

Using the LowPower Library to Save Battery on Arduino

📖 Scenario: You are building a battery-powered Arduino project that needs to save power when it is not doing anything important. To do this, you will use the LowPower library to put the Arduino into sleep mode for a short time.

🎯 Goal: Learn how to use the LowPower library to put the Arduino into sleep mode for 8 seconds repeatedly, saving battery power.

📋 What You'll Learn

Include the LowPower library in your sketch

Use the LowPower.powerDown() function to put the Arduino to sleep

Set up a loop that sleeps for 8 seconds repeatedly

Print a message to the Serial Monitor after waking up

💡 Why This Matters

🌍 Real World

Battery-powered devices like sensors or remote controls need to save power by sleeping when idle.

💼 Career

Understanding power management is important for embedded systems engineers and IoT developers to extend device battery life.

1

Set up the Serial communication

Write void setup() function that starts Serial communication at 9600 baud with Serial.begin(9600); and write an empty void loop() function.

Arduino

void setup() {
  // Your code here
}

void loop() {
  // Your code here
}

Hint

Use Serial.begin(9600); inside setup() to start serial communication.

2

Include the LowPower library

Add the line #include <LowPower.h> at the top of your sketch to include the LowPower library.

Arduino

#include 

void setup() {
  Serial.begin(9600);
}

void loop() {
  
  // Your code here
}

Hint

Use #include <LowPower.h> to add the library.

3

Put Arduino to sleep for 8 seconds

Inside the loop() function, write the line LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF); to put the Arduino to sleep for 8 seconds with ADC and BOD turned off.

Arduino

#include 

void setup() {
  Serial.begin(9600);
}

void loop() {
  // Put Arduino to sleep for 8 seconds
  // Your code here
}

Hint

Use LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF); inside loop().

4

Print a message after waking up

After the sleep line in loop(), write Serial.println("Woke up!"); to print the message each time the Arduino wakes up.

Arduino

#include 

void setup() {
  Serial.begin(9600);
}

void loop() {
  LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
  // Print wake up message
  // Your code here
}

Hint

Use Serial.println("Woke up!"); after the sleep call.

Practice

1.

What is the main purpose of the LowPower library in Arduino?

easy

A. To connect Arduino to the internet

B. To increase the speed of the Arduino processor

C. To add more memory to the Arduino

D. To put the Arduino into sleep mode to save battery power

Solution

1. Step 1: Understand the LowPower library function

   The LowPower library is designed to reduce power consumption by putting the Arduino into sleep mode.

2. Step 2: Compare options with the library purpose

   Options B, C, and D do not relate to power saving or sleep mode, only To put the Arduino into sleep mode to save battery power matches the purpose.

3. Final Answer:

   To put the Arduino into sleep mode to save battery power -> Option D

4. Quick Check:

   LowPower library = Sleep mode for saving power [OK]

Hint: LowPower library = sleep mode to save battery [OK]

Common Mistakes:

• Thinking it speeds up the processor
• Confusing it with memory or internet functions
• Assuming it runs code faster

2.

Which of the following is the correct syntax to put Arduino to sleep for 8 seconds using the LowPower library?

LowPower._____();

easy

A. powerDown(SLEEP_8S, ADC_OFF, BOD_OFF)

B. sleep(8)

C. sleepMode(8)

D. sleepFor(8s)

Solution

1. Step 1: Recall LowPower sleep syntax

   The LowPower library uses powerDown() with parameters for sleep duration and power settings.

2. Step 2: Match correct parameters for 8 seconds sleep

   SLEEP_8S is the constant for 8 seconds, and ADC and BOD are turned off for power saving.

3. Final Answer:

   powerDown(SLEEP_8S, ADC_OFF, BOD_OFF) -> Option A

4. Quick Check:

   LowPower powerDown with SLEEP_8S = correct syntax [OK]

Hint: Use powerDown with SLEEP_8S for 8 seconds sleep [OK]

Common Mistakes:

• Using sleep(8) which is not a LowPower function
• Adding units like '8s' in function calls
• Using incorrect function names like sleepMode

3.

What will be the output on the serial monitor after running this code snippet?

#include <LowPower.h>

void setup() {
  Serial.begin(9600);
  Serial.println("Start");
  LowPower.powerDown(SLEEP_4S, ADC_OFF, BOD_OFF);
  Serial.println("Wake up");
}

void loop() {}

medium

A. Start\nWake up

B. Start

C. Wake up

D. No output

Solution

1. Step 1: Analyze setup() execution

   The code prints "Start", then sleeps for 4 seconds, then prints "Wake up".

2. Step 2: Understand sleep effect on Serial output

   Sleeping pauses the CPU but does not stop the program flow; after sleep, it continues to print "Wake up".

3. Final Answer:

   Start\nWake up -> Option A

4. Quick Check:

   Sleep pauses, then continues printing [OK]

Hint: Sleep pauses but code continues after wake [OK]

Common Mistakes:

• Thinking sleep stops all code permanently
• Expecting no output after sleep
• Confusing sleep with reset

4.

Identify the error in this code using the LowPower library:

#include <LowPower.h>

void setup() {
  LowPower.powerDown(SLEEP_1S, ADC_OFF);
}

void loop() {}

medium

A. powerDown should be called in loop(), not setup()

B. Incorrect library include syntax

C. Missing third parameter for powerDown function

D. SLEEP_1S is not a valid sleep duration

Solution

1. Step 1: Check powerDown function parameters

   The powerDown function requires three parameters: sleep duration, ADC state, and BOD state.

2. Step 2: Identify missing parameter

   The code only provides two parameters, missing the BOD_OFF or BOD_ON parameter.

3. Final Answer:

   Missing third parameter for powerDown function -> Option C

4. Quick Check:

   powerDown needs 3 params: duration, ADC, BOD [OK]

Hint: powerDown always needs 3 parameters [OK]

Common Mistakes:

• Omitting the BOD parameter
• Calling powerDown in setup is allowed
• Assuming SLEEP_1S is invalid

5.

You want your Arduino to sleep for 8 seconds repeatedly until a button press wakes it up. Which code snippet correctly uses the LowPower library to achieve this?

void loop() {
  // Sleep for 8 seconds
  LowPower.powerDown(_____, ADC_OFF, BOD_OFF);
  // Check button press here
}

hard

A. SLEEP_FOREVER

B. SLEEP_8S

C. SLEEP_16S

D. SLEEP_4S

Solution

1. Step 1: Identify sleep duration constant for 8 seconds

   The LowPower library defines SLEEP_8S for 8 seconds sleep intervals.

2. Step 2: Confirm repeated sleep in loop

   Calling powerDown with SLEEP_8S inside loop will sleep repeatedly for 8 seconds until interrupted.

3. Final Answer:

   SLEEP_8S -> Option B

4. Quick Check:

   Use SLEEP_8S for 8 seconds sleep [OK]

Hint: Use SLEEP_8S for 8 seconds sleep in loop [OK]

Common Mistakes:

• Using SLEEP_FOREVER which is not a valid duration
• Choosing invalid SLEEP_16S
• Choosing shorter sleep times like SLEEP_4S